Door-check



J. c. SCHMIDT.

000R CHECK.

APPLICATION FILED MAY 9. 1919.

1,339,479. mm May 11,1920

JOHN C. SCHMIDT, OF CHICAGO, ILLINOIS.

DOOR-CHECK.

Specification of Letters Patent.

Patented May 11, 1920.

Application filed May 9, 1919. Serial No. 295,934.

To all whom it may concern:

Be/it known that I, JOHN C. SCHMIDT, a citizen of the United States, and resident of Chicago, in the county of Cook and 'State of Illinois, have invented certain new and useful Improvements in Door-Checks, of which the following is a specification.

My invention relates to door checks and closers and particularly to a novel liquidless door check similar'in type to that shown in my prior Patent No. 1,266,86 1, of May 21, 1918.

One of the principal objects of the present invention is to provide a construction in which the fluid employed constitutes the sole checking means as distinguished from the construction of my patent heretofore referred to in which the fluid is an auxiliary to a brake which constitutes the primary checking device. One of the principal 0bjections to the employment of air checks has been that the movement of the door toward closing position under the action of a closing spring could not be made uniform, this for the very obvious reason that air being a highly compressible medium could not be caused to offer sufficient resistance to the door during the initial travel of the air compressing piston. Particularly is this true as the closing spring exerts its greatest power when the door is opened, this power being exerted during the initial portion of the closing movement.

I have conceived the idea that the clos ing movement of the door may be made uniform throughout by employing two cylinders and pistons, one of which acts to compress the air and the other to rarefy it. It is well known that vacuum offers high resistance in a properly constructed cylinder and piston, but that upon the admission of a small quantity of air the vacuum is rapidly dissipated, and, as in my device the vacuum resistance takes effect at the point where the spring is exerting its greatest force it conforms strictly to the necessity of the case. As the pistons travel, however, the pressure is built up in the opposite cylinder and by t e time the vacuum cylinder is offering but little resistance the compression cylinder will begin to take effect and as the change from one to the other is gradual the door clesin movement may be made uniform.

b u I a The lnventlon will be more readily understood by reference to the accompanying drawings, wherein,

Figure 1 is a longitudinal sectional view through a device constructed in accordance with my invention, the view being taken on the line 1-1 of Fig. 2, and

Fig. 2 is a sectional view on the line 2-2 of Fig. 1.

In the drawings it will be seen that I provide a casing 10 having attaching flanges 11 and carrying in one portion thereof a container or housing for a door-closing coil spring 12. Centrally mounted within the casing is a winding sleeve 13 which carries the shaft 1 1 to which the door operating arm 15 is secured. At the lower end the shaft has rigidly secured theretoan arm 16 which is connected by links or pitmen 17, 18, to pistons 19, 20. The pistons are adapted to reciprocate within cylinders 21, 22, which in the form shown are secured to the casing 10 by screw threads. The outer ends of the cylinders are closed by caps 23, 24, having air control valves 25, 26 therein. The parts are shown in a position such as would be assumed when the door is in closed position. On the opening movement the pistons 19, 20, will move to opposite positions, the arm 16 traveling through 160. The extent of vacuum and compression will, of course, be controlled by adjustment of the valves 25, 26. It will be noted that these do not function as check valves, but are permanently held in adjusted position. Provided within the pistons 19, 20 are check valves 27, 28, identically disposed with relation to the travel of the pistons. A movement of the pistons to the left as viewed in Fig. 1- that is the movement produced by the opening of the door to which the check is con nectedis free as to both pistons, due to the position of the check valves. On the return movement, however, no air can pass through pistons, the only change in quantity of air being effected by passage through the re stricted apertures controlled by the valves 25, 26.

Ihe closing movement of the door will be uniformly resisted because of the fact that at the beginning of the closing movement there will be created a high degree of vacuum within the cylinder 21. However, as the travel increases this resistance will be reduced as air is admitted through the control valve 25. At the same time the coinpression in the opposite cylinder will progressively increase and will, in fact, be much the highest degree of vacuum is secured during the'initial portion of the stroke or movement of the piston and the degree of vacuum is progressively reduced in the 'ratio which any specified movement of thepiston bears to the total preceding movement. In the opposed cylinder, however, the "reverse is true as the compression is increased according to'the same law: The mechanism described is only necessary where a compressible medium, is utilized, the same problems are not present nor can the same mechanism be used where a liquid is employed.

it will be understood that the principle of employing compression and vacuum might be utilized in a single cylinder and a single piston, the opposite sides of the piston performing the desired functions. This and other modifications, such as will readily sug 'gest themselves to those skilled in the art,

are considered to be within the spirit of my invention.

I claim:

1. "In a pneumatic checking device, the combination of a shaft through which the checking effort is transmitted, a pair of cylinders, pistons in said cylinders, means for transmitting the movement of the pistons to 'theshaft'to rotate thesame, said'pisto'ns being mounted for travel in unison toward opposite ends of said-cylinders, means providing a permanently open, regulably restricted passage between the atmosphere and the interior of each cylinder, and valves permitting unrestricted movement of said pistons in one direction, substantially as described.

'inder's, valves permitting unrestricted movement'of the pistons 111'0116 d1reet1on,"and

means providing apermanently open, regulably restricted passage in the otherwise closed end 0'1": each cylinder, described.

3. In a pneumatic checking device, the

substantially as combination of a shaft through which the checking effort istra-nsm1tted,'apair '0'; cylinders,pistons in said cylinders, a crank'on said shaft, pitmen connecting the'crank "to said pistons, said pistons being so arranged with relation to said crank that in ain'extremepositionthey occupy'opposite ends of their respective cylinders, valves permitting unrestricted movement of the pistons in-one direction, and means providinga permanently open, regulably restricted passage between the atmosphere and the interior of each cylinder, substantially as described.

Signed at Chicago, Illinois, this 6th day of May, 1919.

' JOHN C. SCHMIDT. Witness:

T. D. BUTLER. 

